Nupela Pennsylvanica Guide
Credit: Marina Potapova
  1. Valves linear-lanceolate with parallel or concave margins
  2. Raphe absent on one valve
  3. Striae 26-30 in 10 μm
  4. Axial areas lanceolate
  5. Central area on raphe valve round

Valves are linear-lanceolate with margins that are parallel or slightly constricted in the middle, with subrostrate ends. Striae are slightly radiate throughout the valve, parallel or slightly convergent at the apices, 26-30 in 10 μm. The raphe is absent on one of the valves. Both valves have lanceolate axial areas. The central area on raphe valve is circular and sometimes expanded to the valve margin on one or both sides.